Internal combustion engine



FIG. 1 is a front perspective view of an internal combustion engine showing our new design;

FIG. 2 is a rear perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a right side view thereof; and,

FIG. 8 is a left side view thereof.

Portions of the internal engine shown in broken lines form no part of the claimed design. 

The ornamental design for an internal combustion engine, as shown and described. 